Tap the Websites button under the Allowed Content group.
This displays a list of options: All Websites, Limit Adult Content, and Specific Websites Only.
With Guided Access enabled, your kid won’t be able to close the app, start or switch to another app, or cause mayhem in the Settings app.
The downside, of course, is that your kid may become bored with using one app, so this option works best with deep, engaging apps that will keep your kid entertained for more than a couple of minutes.
Tap Limit Adult Content, and i OS will now block most well-known adult websites automatically. under the Never Allow group, and type in the URL of the website you want to block (such as Simply tap Allow Website, then enter your Restrictions Passcode to add that site to the whitelist.